1. Field of the Invention
The present invention relates to a super magnetostrictive actuator formed by combining at least two super magnetostrictive materials which extend and shrink in the longitudinal direction thereof due to the action of the magnetic field generated by a magnetic field generation means.
2. Description of the Related Art
Of the magnetostrictive materials which generate distortion in the magnetic field, rare earth metal monocrystal such as Tb (terbium), Dy (dysprosium) or the like known as super magnetostrictive material generates enormous magnetostriction which is about several hundred times as that generated by general magnetostrictive material such as Ni, Co or the like. Since TbFe.sub.2 or DyFe.sub.2 which is a binary alloy of Tb and Fe or Dy and Fe is able to generate enormous magnetostriction in the room temperature, such a binary alloy is used as a source for driving an actuator. However, enormous magnetostriction generated by such super magnetostrictive materials only exceeds the displacement of about 0.1% at most. Thus, in order to secure a required output displacement while avoiding the enlargement of the size of the actuator, it is required to combine a plurality of super magnetostrictive materials so as to accumulate slight extension and shrinkage amounts of the respective super magnetostrictive materials thereby to output the accumulated displacement.
Such a super magnetostrictive actuator for securing a required output displacement by combining a plurality of super magnetostrictive materials in this manner is known as disclosed in Japanese Patent Unexamined Publication NO. Hei.4-168984.
However, the aforesaid conventional super magnetostrictive a actuator is arranged in a manner that a plurality of super magnetostrictive materials formed in a column shape are disposed along the inner periphery of a coil formed in a cylindrical shape, and the end portions of the adjacent super magnetostrictive materials are coupled to each other by a link which is supported at its center portion by a fulcrum. According to the actuator thus arranged, an amount of extension and shrinkage of each of the super magnetostrictive materials is transmitted to the adjacent super magnetostrictive material through the link mechanism thereby to generate a required output displacement between the super magnetostrictive materials positioned at both ends.
However, in the conventional actuator, since the plurality of super magnetostrictive materials are coupled by the link mechanism, the number of the parts such as the link member and the fulcrum thereof etc. increases and the number of assembling processes thereof also increases. As a result, the cost of the actuator increases, and further the actuator may be prevented from moving smoothly since the magnitude of friction and the degree of wobble at a movable portion and a sliding portion increase.